1. Field of the Invention
The present invention relates to an adhesive film and an image display device and, more particularly, to an adhesive film used in various industrial fields such as electrics and electronics, semiconductors and optics, and an image display device comprising the adhesive film.
2. Description of the Background Art
It has hitherto been known that an adhesive film comprising a base material and an adhesive layer formed on the base material is stuck onto parts so as to protect parts in a dicing or grinding step in case of producing parts in the fields such as electrics and electronics or semiconductors. This adhesive film is usually removed after the completion of the protection of parts.
However, when the adhesive film is removed from the parts, static electricity (so-called static charge on peeling), between the adhesive film and parts, is generated thereby, to cause problems such as an adverse influence exerted on a circuit of parts and adhesion of dust and rubbish.
Also it has hitherto been known that an adhesive film is stuck onto parts so as to protect parts in a production process in the case of producing parts in the optical fields. This adhesive film is usually removed after being stuck onto a liquid crystal display (LCD).
However, when the adhesive film is removed from the liquid crystal display, static charge on peeling is generated thereby to cause problems of disturbing the liquid crystalline order and images.
Therefore, there is proposed, as an adhesive film including an adhesive optical film capable of preventing the above-mentioned static charge on peeling, an antistatic adhesive film comprising a base material film, an antistatic layer comprising a tin oxide-based, indium oxide-based or zinc oxide-based conductive filler and an organic binder and formed on one principal surface of the base material film, and an adhesive layer formed on a surface of the antistatic layer (see, for example, Japanese Unexamined Patent Publication No. 8-245932).
However, in the antistatic adhesive film proposed in Japanese Unexamined Patent Publication No. 8-245932, it becomes difficult to sufficiently secure adhesion between the base material film and the adhesive layer.
Heretofore, optical films such as polarizing film, phase difference film, luminance improving film, and view-angle expansion film have been used for various industrial purposes and, for example, these optical films are used for sticking onto image display devices such as a liquid crystal display (LCD), organic electroluminescence device (organic EL display device), and plasma display panel (PDP).
As the optical film to be stuck onto these image display devices, an adhesive optical film comprising an optical film laminated with an adhesive is known.
In view of the environmental burden, it has recently been required to reduce the use of an organic solvent, and a solvent-based adhesive containing an organic solvent as a solvent is desired to be replaced by a water dispersible adhesive containing water as a dispersion medium.
As such, the water dispersible adhesive, for example, there is proposed a pressure sensitive adhesive composition comprising a copolymer emulsion in which a copolymer contains 2-ethylhexyl methacrylate of an amount of 10 to 50% by weight based on the entire copolymer and the copolymer has a glass transition temperature of −25° C. or lower (see, for example, Japanese Unexamined Patent Publication No. 2001-254063).
A surface protective film is stuck onto a surface of the adhesive optical film so as to prevent scratches and fouling on the surface of the adhesive optical film in the production process and the following transportation process, and the adhesive optical film is stuck onto the image display device in this state. When the transportation process of the image display device is completed, the surface protective film is usually removed from the adhesive optical film.
However, when the surface protective film is removed from the adhesive optical film, static electricity (so-called static charge on peeling), between the adhesive optical film and the surface protective film is generated thereby to cause disturbance of liquid crystalline order and breakage of a circuit of the image display device onto which the film is stuck, thus resulting in a problem of disturbance of images.
Therefore, there is proposed, as an adhesive film including an adhesive optical film capable of preventing the above-mentioned static charge on peeling, an antistatic adhesive film comprising a base material film, an antistatic layer comprising a tin oxide-based, indium oxide-based or zinc oxide-based conductive filler and an organic binder and formed on one principal surface of the base material film, and an adhesive layer formed on the surface of an antistatic layer (see, for example, Japanese Unexamined Patent Publication No. 8-245932).
However, an adhesive film comprising a conventional water dispersible adhesive including those disclosed in Japanese Unexamined Patent Publication No. 2001-254063 show particularly low adhesion to a hydrophilic adherend such as glass and therefore it has difficulty to firmly stick onto a glass substrate of a liquid crystal display, although adhesion to a hydrophobic adherend such as polyolefin is improved.
Further, with respect to a water dispersible adhesive to be laminated on an optical film, excellent heat resistance and moisture resistance, which results in preventing deterioration of adhesion due to severe heating and humidifying, are required.
Furthermore, in the antistatic adhesive film proposed in Japanese Unexamined Patent Publication No. 8-245932, it becomes difficult to sufficiently secure adhesion between the base material film and the adhesive layer.